The present invention is directed to a pressure modulating valve assembly and more particularly to an electrically operated valve supporting member which is mounted in rolling contact with a yoke of a solenoid coil in response to the operation of the solenoid coil to modulate pressure in a valve chamber.
A conventional pressure modulating valve is disclosed in U.S. Pat. No. 4,249,457, granted Feb. 10, 1981, and entitled "Vacuum Servomotor". In the conventional pressure modulating valve assembly, an armature of magnetic material having recesses at opposite sides thereof is pivoted on a yoke member by means of upstanding projections formed at opposite sides of the yoke whereby the projections are loosely fitted within the recesses, respectively. A valve supporting member of non-magnetic material is secured to the armature and is provided with valve members at opposite ends thereof. Spring means are provided for biasing the armature to a first position wherein one of the valve members engages a valve seat and a solenoid coil is provided for biasing the armature to a second position against the force of the spring means to move the other valve member into engagement with a valve seat while moving the first mentioned valve member out of engagement with its respective valve seat. In the foregoing arrangement, the durability of the valve is lessened since the recesses of the armature and the projections on the yoke are quickly worn by the constant rubbing action which occurs on every rotation of the armature. Such wear eventually leads to undesirable tolerances which adversely affect the seating of the valve members on their respective seats.
In co-pending U.S. patent application Ser. No. 404,738, filed Aug. 3, 1982, now U.S. Pat. No. 4,446,889 which is assigned to the same assignee as the present application, a new and improved pressure modulating valve assembly was disclosed comprising a solenoid coil, yoke means having curved support surfaces extending from one end of said coil to the other, resilient non-magnetic valve supporting means having at least one valve secured thereto, and attaching leg means secured to said yoke means in overlying relation relative to said curve supporting surfaces, an armature of magnetic material secured to said valve supporting means at a central portion thereof spaced from the point of attachment of said valve supporting means to said yoke means and spring means normally biasing said armature in a direction away from said solenoid coil whereby upon energization of said coil, said solenoid supporting means and said armature secured thereto are subjected to a rolling motion along the curved surface of said yoke means to provide a friction-free connection between said yoke means and said combined armature and valve support means.
Such a valve is generally used as an exhaust gas recirculation system valve (EGR valve) in automobiles. The purpose of using such a valve is to generate an intermediate or middle level vacuum between the atmospheric pressure and the intake manifold vacuum. It is important to have a stable operational characteristic for this type of valve and the individual valve elements must be brought into air tight contact with the ports. As shown in FIG. 1 of the present application, a conventional type valve, which is only partially illustrated, is provided with a valve element 23 attached to an elastic plate 21. When an electromagnetic coil, such as that disclosed in application Ser. No. 404,738, is energized, the right side of the movable piece 20 is moved downwardly overcoming the force of the spring 24. Thus, the elastic plate 21, which is secured to the middle piece 20, is rotated about a point on the arm 19a of the yoke 19 to bring the element 23 into contact with the valve 4. Due to the location of the yoke 19 upon which the valve member is mounted relative to the valve port, the contact of the sealing surface 23a of the valve element 23 with the valve seat which surrounds the port 15 is linear, thus making an incomplete seal relative to the port which will allow the leakage of air past the valve element.